Alloy



Patented Aug. 16, 1938 YUNirEo STATES PATENT OFFICE Annoy Anthony G,'deGolyer, New York, N. Y.

- No Drawing. Appllcation August 25, 1936,

Serial No. 97,815 i 3 Claims. (Cl. 148 32) cuttingtools, the cuttingeiliciency of which is 10' superior to that of present known high speedsteels and other alloys. A further object is to provide an alloy whichis free from, or substantially free from carbon and which is readily,amenable to thermal treatment, by means of I 16 which the hardness,tensile strength, cutting efficiency and other physical properties andcharacteris'tics may be accurately controlled over a comparatively widerange.

I have found through experiment that by al- 20 loying or otherwiseintimately combining boron,- tungsten; vanadium, chromium, zirconium andcobalt within the range of boron 0.50% to 3%,

tungsten 5% to 30%, vanadium 1% to 8%, zir-' hardness, resistance toimpact and certain other important physical properties can be developedonly through thermal treatment, or through me 35 chanical working andsubsequent thermal treatment. Bodies of the alloys which have beensubsensitive to various operating conditions as to greatly restrictthe'scope of usefulness. One of the greatest disadvantages of suchheretofore proposed compositions is that none of them are responsive tothermal treatment for regulation of physical properties, andconsequently physical properties and characteristicsare governedentirely by the chemical composition of the sintered or cast material. I

My alloy may be used in the asvcast condition, 10

or it may be forged or otherwise mechanically worked. In either case Iprefer to subject the, alloy to thermal treatment before using it as acutting tool or die. Both the cast .and forged material are equallyamenable to thermal treatment. For example, cast bodies of this alloymay have a hardness of from 50 to 60 on the Rockwell C. scale and bysubjecting the material. to suitable thermal treatment, such asquenching from a temperature higher than approximately 1,000 C., thehardness may be lowered to anapproximate range of from 40 to 47 RockwellC. In this condition the bodies may be ground, shaped or formed) asdesired. The alloy may subsequently be submitted to a second thermaltreatment, such as heating to a temperature of less than 1,000 C. for aperiod of one hour or more, by which the hardness may be increased tofrom approximately 60 to 70 Rockwell C. In the latter condition thealloy is especially valuable for the cutting or mechanical working of alarge number of metals and alloys, as well as numerous non-metallicmaterials. An important property of this alloy is that virtually all -ofthe maximum hardness, developed by thermaltreat- 5,

J ment, is retained when the alloy is subjected to I .jected to suchtreatment are particularly valu-J elevated temperatures. s. uch as aregenerthan such steel," all of them have disadvantages which render themunsuitable for general application asmetal 'cutting or forming tools.Compositions containing principally carbides of tungsten, molybdenum ortantalum bonded with a v relatively soft matrix metal have a high degreeof hardness, but are extremely brittle. Cast compositions of the typesheretofore proposed require the presence of at least 1.50% carbon toqualify as metal cutting tools and, as is' well known, such alloys arenot only brittle, butare so ated in the tip of a tool cuttingmetal at.high speed. Although the alloy has a high degree of hardness andresistance to abraslon by hot metal; 40 chips, especially after thermaltreatment, it is remarkablyresistant to failurefrom sudden or repeatedshock. "Therefore, tools made of the present alloy retain an efficientcutting edge for I longer periods than other tools. I 5

,The more important distinctive and valuable advantages are, apparently,due to the presence of appreciable amounts of .boron in-the compo--sition, in conjunction with the other essential component elementswithin the percentagesspec ified herein,

I have. found that molybdenum may .beused to supplant all or a portionof the tungsten of the present alloy. Likewise, uranium may be used inplace of either tungsten or molybdenum.

Specific examples of compositions within the scope of the presentinvention which I have found well adapted for metal cutting tools, diesand the like are the following: boron 1.20%, tungsten 14%, vanadium2.75%, chromium 5%, zirconium 1.45%, cobalt balance; boron 2.10%,tungsten 19.50%, vanadium 4%, chromium 4%, zirconium 0.80%, cobaltbalance; boron 1.65%, molybdenum 13%, vanadium 3.50%, chromium 3.5%,zirco-' nium 3.75%, cobalt balance; boron 1.70%, tungsten 5%, molybdenum10%, vanadium 5%, chromium 8%, zirconium 4.6%, cobalt balance; boron1.10%, molybdenum 12%, vanadium 6%, chromium 7%, zirconium 1.75%, cobaltbalance.

An objective of the present invention is to provide alloys having highhardness, high resistance to shock and impact, advantageous metalcutting properties, etc., which are free or substantially free fromcarbon, and thus eliminate all of the serious disadvantages associatedwith carbon containing non-ferrous alloys or compositions intended formetal cutting tools. Although I prefer to have the alloys of thisinvention entirely free from carbon, in many instances I have foundcarbon present in the nature of an impurity incidental to manufacture.It is important to restrict the amount of carbon so present to a maximumof about 0.15%, as I have found that the presence of higher percentagesof this element make the alloy extremely brittle and subject to failureduring cutting operations, and, greatly retards or entirely prevents thedesired and necessary reactions during thermal treatment. Furthermore,the presence of appreciable amounts of carbon decreases the red hardnessof the alloy, i. e. hardness at temperatures of approximately 550 C. andhigher.

By reason of the fact that the elements forming the essential componentsof the alloy of the present invention invariably are contaminated withother elements when produced in commercial quantities, the alloys of myinvention usually contain insignificant amounts of one or more elementsin the nature of impurities incidental to manufacture. Because of thefact that the maximum values of physical properties of the present alloycan be developed only through thermal treatment, it is essential thatthe amount of such incidental impurities present be limited topercentages which will not be'efiective in retarding,

or entirely preventing the necessary physical reactions during thermaltreatment. Further, the

percentages of such impurities should also be restricted to amountswhich will not be effective on the physical properties orcharacteristics of the alloy either before or after thermal treatment.

I have found that the most harmful impurities commonly present, inaddition to carbon, are silicon and aluminum. The presence of either ofthese elements in amounts greater than approximately 1% renders thealloy of the present invention entirely unsuitable for thermal treatmentby means of. which the hardness, tensile strength and with one or moreof the essential components of the present'alloy, and such compounds arenot only hard, brittle and lacking in impact resistance, but arevirtually insoluble in the solid composition during thermal treatment.It will be apparent, therefore, that the presence of effective amountsof impurities, such as carbon, silicon and aluminum, materially changethe character of the alloy through rendering it not amenable to thermaltreatment.

My investigations indicate that the preferred structure of a body of thepresent alloy is produced only by means of thermal treatment, and thatthis comprises at least two principal constituents: one, a relativelyhard intermetallic compound of boron with one or more of the otheressential components; and, second, a solid solution of two or more ofthe essential components which has a lower degree of hardness andfunctions as a matrix. In some instances the structure will contain athird constituent in the nature of an eutectoid. The ratio of theconstituents and the ratio of particle size in any particular body ofthe alloy may be accurately controlled and fixed over a wide range bymeans of thermal treatment, or mechanical working and subsequent thermaltreatment.

By reason of the combined advantageous physical properties possessed bythe alloy of the present invention, tools and other articles composed ofthis alloy may be operated efliciently and economically under conditionswhich are impossible or unecoriomical with tools or articles composed ofheretofore known alloys or metallic compositions.

By the term the balance substantially cobalt in the foregoing and in thefollowing claims, I intend that the alloy of, the present inventioncomprises boron, vanadium, zirconium, chromium and metal of the grouptungsten, molybdenum and uranium, within the percentage limitsspecified, with the remainder cobalt except for ineffective amounts ofimpurities which may be present incidental to manufacture, ashereinbefore explained.

I claim: x

1. A precipitation hardened alloy containing boron 0.50% to 3%, metalfrom the group tungsten, molybdenum and uranium 5% to 30%, vanadium 1%to 8%, zirconium 0.25% to 5%, chromium 1% to 25%, the balance cobalt.

- 2. A precipitation hardened alloy containing boron 0.50% to 3%,tungsten 5% to 30%, vanadium 1% to 8%, zirconium 0.25% to 5%, chromium 1to 25% the balance cobalt.

3. A precipitation hardened alloy containing boron 0.50% to 3%,molybdenum 5% to 30%, vanadium 1% to 8%, zirconium 0.25% to 5%,

. chromium 1% to 25%, the balance cobalt.

ANTHONY G. DE GOLYER.

